[PATCH v2 01/11] static_call: Improve key type abstraction

Josh Poimboeuf
2023-03-22T04:00:34Z

Make the static_call_key union less fragile by abstracting all knowledge
about the type bit into helper functions.

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
---
include/linux/static_call_types.h | 4 +-
kernel/static_call_inline.c | 51 +++++++++++++++++--------
tools/include/linux/static_call_types.h | 4 +-
3 files changed, 40 insertions(+), 19 deletions(-)

diff --git a/include/linux/static_call_types.h b/include/linux/static_call_types.h
index 5a00b8b2cf9f..87c3598609e8 100644
--- a/include/linux/static_call_types.h
+++ b/include/linux/static_call_types.h
@@ -63,8 +63,8 @@ struct static_call_key {
union {
/* bit 0: 0 = mods, 1 = sites */
unsigned long type;
- struct static_call_mod *mods;
- struct static_call_site *sites;
+ struct static_call_mod *_mods;
+ struct static_call_site *_sites;
};
};

diff --git a/kernel/static_call_inline.c b/kernel/static_call_inline.c
index 639397b5491c..41f6bda6773a 100644
--- a/kernel/static_call_inline.c
+++ b/kernel/static_call_inline.c
@@ -112,15 +112,21 @@ static inline void static_call_sort_entries(struct static_call_site *start,

static inline bool static_call_key_has_mods(struct static_call_key *key)
{
- return !(key->type & 1);
+ return !!(key->type & 1);
}

-static inline struct static_call_mod *static_call_key_next(struct static_call_key *key)
+static inline struct static_call_mod *static_call_key_mods(struct static_call_key *key)
{
if (!static_call_key_has_mods(key))
return NULL;

- return key->mods;
+ return (struct static_call_mod *)(key->type & ~1);
+}
+
+static inline void static_call_key_set_mods(struct static_call_key *key, struct static_call_mod *mods)
+{
+ key->_mods = mods;
+ key->type |= 1;
}

static inline struct static_call_site *static_call_key_sites(struct static_call_key *key)
@@ -128,7 +134,12 @@ static inline struct static_call_site *static_call_key_sites(struct static_call_
if (static_call_key_has_mods(key))
return NULL;

- return (struct static_call_site *)(key->type & ~1);
+ return key->_sites;
+}
+
+static inline void static_call_key_set_sites(struct static_call_key *key, struct static_call_site *sites)
+{
+ key->_sites = sites;
}

void __static_call_update(struct static_call_key *key, void *tramp, void *func)
@@ -154,7 +165,7 @@ void __static_call_update(struct static_call_key *key, void *tramp, void *func)
goto done;

first = (struct static_call_mod){
- .next = static_call_key_next(key),
+ .next = static_call_key_mods(key),
.mod = NULL,
.sites = static_call_key_sites(key),
};
@@ -250,8 +261,7 @@ static int __static_call_init(struct module *mod,
* static_call_init() before memory allocation works.
*/
if (!mod) {
- key->sites = site;
- key->type |= 1;
+ static_call_key_set_sites(key, site);
goto do_transform;
}

@@ -266,10 +276,10 @@ static int __static_call_init(struct module *mod,
*/
if (static_call_key_sites(key)) {
site_mod->mod = NULL;
- site_mod->next = NULL;
site_mod->sites = static_call_key_sites(key);
+ site_mod->next = NULL;

- key->mods = site_mod;
+ static_call_key_set_mods(key, site_mod);

site_mod = kzalloc(sizeof(*site_mod), GFP_KERNEL);
if (!site_mod)
@@ -278,8 +288,9 @@ static int __static_call_init(struct module *mod,

site_mod->mod = mod;
site_mod->sites = site;
- site_mod->next = static_call_key_next(key);
- key->mods = site_mod;
+ site_mod->next = static_call_key_mods(key);
+
+ static_call_key_set_mods(key, site_mod);
}

do_transform:
@@ -406,7 +417,7 @@ static void static_call_del_module(struct module *mod)
struct static_call_site *stop = mod->static_call_sites +
mod->num_static_call_sites;
struct static_call_key *key, *prev_key = NULL;
- struct static_call_mod *site_mod, **prev;
+ struct static_call_mod *site_mod, *prev;
struct static_call_site *site;

for (site = start; site < stop; site++) {
@@ -416,15 +427,25 @@ static void static_call_del_module(struct module *mod)

prev_key = key;

- for (prev = &key->mods, site_mod = key->mods;
+ site_mod = static_call_key_mods(key);
+ if (!site_mod)
+ continue;
+
+ if (site_mod->mod == mod) {
+ static_call_key_set_mods(key, site_mod->next);
+ kfree(site_mod);
+ continue;
+ }
+
+ for (prev = site_mod, site_mod = site_mod->next;
site_mod && site_mod->mod != mod;
- prev = &site_mod->next, site_mod = site_mod->next)
+ prev = site_mod, site_mod = site_mod->next)
;

if (!site_mod)
continue;

- *prev = site_mod->next;
+ prev->next = site_mod->next;
kfree(site_mod);
}
}
diff --git a/tools/include/linux/static_call_types.h b/tools/include/linux/static_call_types.h
index 5a00b8b2cf9f..87c3598609e8 100644
--- a/tools/include/linux/static_call_types.h
+++ b/tools/include/linux/static_call_types.h
@@ -63,8 +63,8 @@ struct static_call_key {
union {
/* bit 0: 0 = mods, 1 = sites */
unsigned long type;
- struct static_call_mod *mods;
- struct static_call_site *sites;
+ struct static_call_mod *_mods;
+ struct static_call_site *_sites;
};
};

--
2.39.2